In general, inkjet printing machines or printers include at least one printhead that ejects drops or jets of liquid ink onto a recording or image forming surface. In some inkjet printers, the printhead ejects ink directly onto the surface of media as the media passes the printhead. The media can be in the form of a continuous web or in the form of sheets. In continuous web printers, the media is pulled from a supply roll by actuator-driven rollers. As the web moves through the printer it passes around rollers to which tension is applied to keep the web taut as it passes through the printer to a take-up roll. In sheet printers, actuator-driven rollers are positioned against one another to form nips and these nips urge the sheets through the printer.
In inkjet printers that eject ink directly onto sheets, media deformation occurs more frequently in sheet printers than continuous web printers since a web is generally taut as it passes through the printer. Sheets having leading and trailing edges that can get caught in structure and wrinkled. Additionally, the sheets can absorb moisture in the inks ejected onto the sheets and this moisture can cause curling or other deformations in the media. These deformations are particularly troublesome in inkjet printers that employ water-based or solvent-based inks in which pigments or other colorants are suspended or in solution. The water and solvents in the inks can change the physical properties of the sheets in ways that degrade the quality of the images produced on the media sheets. Consequently, most aqueous ink printers form the ink images on a blanket mounted to a drum or endless belt and then transfer the ink image to media sheets as they pass through a nip formed with the drum or endless belt. Such a printer avoids the changes in image quality, drop spread, and media properties that occur in response to media contact with the water or solvents in aqueous ink. Addressing the media property changes would enable inkjet printers to eject ink directly onto media without adversely impacting image quality.